(1) Field of the Invention
The present invention relates to a liquid crystal display device, and in particular, to a technology which is effective when applied to a liquid crystal display device where one display region is divided in two: a top region and a bottom region.
(2) Related Art Statement
Conventional liquid crystal display devices include liquid crystal televisions and liquid crystal displays connected to PC's (personal computers). The above described liquid crystal displays devices, such as liquid crystal televisions, usually display videos and images (that is to say, videos and still images) in a drive system, referred to as active matrix.
In liquid crystal display panels used in the above described active matrix type liquid crystal display devices, one display region is made up of a set of pixels having TFT elements and pixel electrodes, for example. The above described liquid crystal display panels are display panels where a liquid crystal material is sealed between a pair of substrates, and a number of scanning signal lines, a number of video signal lines, a number of TFT elements and a number of pixel electrodes are arranged on one of the above described pair of substrates (hereinafter referred to as TFT substrate). In addition, a light blocking film in net form which extends to such locations as to face the above described number of scan signal lines on the above described TFT substrate and in such locations as to face the above described number of video signal lines and a color filter, for example, are arranged on the other of the pair of substrates (hereinafter referred to as facing substrate).
In addition, counter electrodes which make pairs with the above described pixel electrodes when the liquid crystal molecules in the above described liquid crystal material are controlled (may be referred to as common electrodes) may be arranged on the above described TFT substrate or on the above described facing substrate, depending on the control method for the above described liquid crystal molecules.
In addition, in general active matrix type liquid crystal display panels, the gates of TFT elements of a number of pixels aligned in the direction in which the above described scanning signal lines extend are connected to one common scanning signal line in one display region. In addition, in general active matrix type liquid crystal display panels, the drains of TFT elements of a number of pixels aligned in the direction in which the above described video signal lines extend are connected to one common video signal line in one display region.
In addition, the screen size of liquid crystal display devices, such as liquid crystal televisions, has been increasing in recent years, that is to say, the area of one display region in the liquid crystal panels used has been increasing. In addition, the resolution of liquid crystal display devices, such as liquid crystal televisions, has been increasing in recent years, that is to say, the number of pixels that form one display region in the liquid crystal display panels used has been increasing. Therefore, in conventional, general liquid crystal display devices, for example liquid crystal display devices having signal input terminals for scanning signal lines only on the left of one display region and signal input terminals for video signal lines only at the top, the difference in delay of signals applied to a scanning signal line or a video signal line becomes great between pixels which are close to the signal input terminals and those which are and far away, and thus, the image quality tends to lower.
In order to prevent the picture quality from lowering as describe above, signal input terminals for scanning signal lines have been provided on the left and right of one display region, and signal input terminals for video signal lines provided on the top and bottom in liquid crystal display devices, for example, in recent years.
In addition, in the case where signal input terminals for video signal lines are provided on the top and bottom of one display region, one display region is divided into an upper region and an upper region along a border line in the direction in which the scanning signal lines extend, and the video signal lines connected to the drains of TFT elements of pixels which belong to the first display region above the above described border line and the video signal lines connected to the drains of TFT elements of pixels which belong to the second display region below the above described border line are electrically isolated from each other. In this configuration, videos and images can be displayed side-by-side in the above described first display region and the above described second display region. Therefore, the time required to display one frame for a video or an image becomes half of in the prior art, and thus, it becomes easy to deal with increase in the speed of display.
In the case where one display region is divided in two: a top region and a bottom region as described above, however, the image quality changes a great deal along the above describe border line, and the image quality may lower. Thus, various methods for preventing the image quality from lowering along the border line have been proposed for liquid crystal display devices where one display region is divided in two: a top region and a bottom region, so that videos and images are displayed in parallel on the above described first display region and the above described second display region (see for example Patent Document 1 and Patent Document 2).    (Patent Document 1) Japanese Unexamined Patent Publication H10 (1998)-268261    (Patent Document 2) Japanese Unexamined Patent Publication H8 (1996)-22028